Thermostatic mixing valves are used in a variety of applications for mixing fluids of dissimilar temperatures to produce a tempered fluid discharge output temperature. For example, and in one illustrative application, thermostatic mixing valves are commonly used in conjunction with water heaters. Water heaters are frequently used to supply hot water to desired locations within a house, office building, or other structure. To regulate the temperature of water discharged by the water heater, a thermostatic mixing valve can be connected to the hot water outlet of the water heater, allowing hot water discharged from the water heater to be mixed with cold water supplied to the structure to produce a relatively constant tempered discharge output temperature. The tempered water discharged from the mixing valve can be fed into the structure's hot water piping for subsequent use by the occupants. Such mixing valves are typically configured such that the temperature of the mixed water remains constant or nearly constant regardless of the temperature and flow rate of the hot and cold water supplied to the mixing valve.
With the construction of larger homes and an increased usage of hot water, the demand for water heaters having larger heating capacities has grown significantly. Some water heaters are configured to produce hot water that is at a temperature that is significantly hotter than that desired in the structure's hot water piping. By increasing the temperature of the water supplied by the water heater, a greater amount of cold water may be mixed with the hot water to increase the effective heating capacity of the water heater. Some thermostatic mixing valves have a temperature adjustment mechanism that allows a contractor or other personnel to adjust the discharge water temperature that is produced at the output of the mixing valve. In some instances, it may be desirable to include an optional secondary hot port for providing hot water directly to an appliance or other fixture that can use non-tempered hot water (e.g. water provided directly from a water heater or the like).